Structural Engineering

Materials

Rubric

• Rubric:• Bridge efficiency:

40pts• Thumbnail sketches

15pts• Final Drawing

20pts• Bridge Quiz

25pts

• Bridges must be able to withstand several types of forces. The two most common to model bridges are compression and tension, pushing and pulling respectively. The other two are torsion (twisting) and shear. Learn what these forces mean so that you can build a better model bridge.

Compression

Tension

Torsion

Shearing

• Racking

Biology Connection

• Balsa Wood

• Ochroma pyramidale

• A member of the mallow family, O. pyramidale is native to southern Brazil and northern to southern Mexico, but is now found in many other countries (Papua New Guinea, Indonesia, Thailand, Solomon Islands). It is a pioneer plant, which establishes itself in clearings in forests, either man-made or where trees have fallen, or in abandoned agricultural fields. It grows extremely rapidly, up to 90 ft (30 m) in 10–15 years. The speed of growth accounts for the lightness of the wood; balsa wood has a lower density than cork. Trees frequently do not live beyond 30 to 40 years

Archways

• Transferring weight (load)

Gateway Arch

hyperbolic cosine function describes the shape of a catenary

Weighted catenary

• Both the width and height of the arch are 630 feet (192 m). The arch is the tallest memorial in the United States and the tallest stainless steel monument in the world.

• The cross-sections of the arch's legs are equilateral triangles, narrowing from 54 feet (16 m) per side at the bases to 17 feet (5.2 m) per side at the top. Each wall consists of a stainless steel skin covering a sandwich of two carbon-steel walls with reinforced concrete in the middle from ground level to 300 feet (91 m), with carbon steel to the peak. The arch is hollow to accommodate a unique tram system that takes visitors to an observation deck at the top.

Arc de Triomphe, or Arch of Triumph

• Commissioned by Napoleon in honor of his conquests

• Eggs are similar in shape to a 3-dimensional arch, one of the strongest architectural forms. The curved form of the shell distributes pressure evenly all over the shell rather than concentrating it at any one point.

• By completely surrounding the egg with your hand, the pressure you apply by squeezing is distributed evenly all over the egg. However, eggs do not stand up well to uneven forces which is why they crack easily on the side of a bowl.

Materials

• Must have box (container)

• Located on the long table

• One bundle of Balsa

• Five pins

• One index card (gusset material)

• One ruler

• One bottle of glue